Sick chin help!

Please help, I am a desperate chin mommy! I have had a sick chin for about 3-4 weeks now. shallow breathing, very little appetite. He will eat a little critical care 1-2 times a day. We have been back and fourth to the 2 different vets and aside from spending hundreds more on top of the $400I have already spent they are telling me there isn't much I can do. I was giving him an oil to help him poop and a medication to promote mobility in the stomach. I had xrays done and his heart, teeth and lungs look great. His stomach is very bloated. He was almost better and started eating a little of his regular food and drinking water again. Now all the sudden he lost 80 grams and we are back where started. the vet gave me a medication for bloating an some pain medication along with fluids last night. I got him to eat a ton of critical care last night. Today back to eating nothing. So desperately I googles some more natural solutions and I am trying the pineapple juice. I also read that papaya can increase appetite so I tried that. well he loves the papaya and started eating a little again today. I was alternating tiny papaya pieces with the critical care. My question is should I let him eat as much of the papaya as I can get in him at this point? I know chins should not have a lot of sugar or treats so I am nervous to continue with it. Any other suggestion would be great as vet told me I should put him down yesterday but I just don't feel its time. I had him feeling much better last week. the heavy breathing had quit and he was drinking a little water and eating some pellets. Also he is pooping they are just small. He is 10 years old and such a sweet chin, we just aren't ready to put him down just yet. :(:(:(